Various devices have heretofore been utilized in rotary balers for severing twine after the latter has been wrapped around a bale along the length thereof just prior to ejecting the bale from the baler. For a variety of reasons, however, numerous of these devices have been less than satisfactory. For example, stationary devices simply presenting one or more sharp edges have been utilized so that no moving parts requiring manual or automatic actuation and periodic servicing are involved. In balers employing such cutters the twine is simply drawn across the sharp edge of the cutter at the close of the bale-wrapping cycle with the hope that the tension in the twine will be sufficient to cause the twine to become severed as it is drawn across such knife edge.
It has been found in such stationary cutters, however, that there is little practical way of clearing trash and crop materials from the cutter which may accumulate during normal operating cycles of the baler and, as may be expected, such materials can and do interfer to a significant degree with the ability of the twine to come into proper severing engagement with the sharp edge of the cutter. When that occurs, the twine simply fails to sever and, if the operator notices the malfunction, he is then required to climb down out of the operator's position, walk to the baler, manually sever the twine and likewise manually clean out the cutter.
Other types of cutters have employed scissor-like components to snip the twine in two as the wrapping cycle is completed, but as in the case of the stationary cutters, it has not been unusual for such scissor-like cutters to become clogged with trash and other materials which require periodic cleanout in order to avoid malfunction. Moreover, scissor cutters are particularly dependent upon having a high degree of tension in the twine at the time of severance.
Desirably, the twine severance is carried out automatically so that the operator need not pay particular attention to the wrapping cycle per se and the position of the twine dispensing member relative to the end of the bale. Such automatic severance is quite old in the art such as shown, for example, in Berge U.S. Pat. No. 2,627,223; Harrer U.S. Pat. No. 2,850,964; and Luebben U.S. Pat. No. 3,064,556. There the cutter is actuated when the twine dispensing tube approaches its home position. However, one shortcoming with the approach of actuating the cutter according to twine tube position lies in the fact that the twine itself may not be perfectly oriented or properly tensioned at the particular instant that the dispensing tube triggers the cutter and, in that eventuality, the twine may fail to be severed.